1. Field of the Invention
The present invention relates to an electrophotographic copying machine, to be particular, it relates to an electrophotographic copying machine having an operation mode in which a mirror scanner stops at a light transmission part of a platen glass being covered with a covering member such as an original holder, an automatic document feeder, etc.
2. Description of the Prior Arts
This kind of electrophotographic copying machine is, for example, described in U.S. Pat. No. 4,057,341. The machine has a mirror scan mode in which copying is performed by scanning an original image on a platen glass with a mirror scanner and a Leaf Document Circulation Mode (LDC mode) in which copying is performed by scanning an image while an original is conveyed on a platen glass and a mirror scanner is stopped at a light transmission part of the platen glass. During the period in which the LDC mode is set, the mirror scanner is moved to the light transmission part of the platen glass and it stays there keeping the state where copying is possible.
When an original being conveyed is jammed on the platen glass in the state where the LDC mode is possible, for the processing of the jam, a covering member such as the automatic document feeder or the original holder for covering the platen glass can be opened.
As the mirror scanner is made to position and stay at the light transmission part of the platen glass, if the covering member is opened, the mirror scanner catches the light incident on the platen glass. The light is led to a part of a photosensitive member through an exposure optical system including the mirror scanner and locally exposes the photosensitive member. Thus, local optical fatigue can occur in the photosensitive member; it can cause uneven electric charging in the following image formation, and furthermore it causes unevenness in the density of an image formed on a copyng paper.